RE: Fw: Applying Sereno's definitions to Neotetanurae Part 1

["Jaime A. Headden" <qilongia@yahoo.com>]

Mickey Mortimer (mickey_mortimer111@msn.com) wrote:

<Although Holtz has sixteen characters supporting placing Bagaraatan outside
Tyrannosaurinae, only seven are valid- straight pubis (probably true, though
the missing distal end makes it a bit uncertain);>

  Indeed, since no one has, to date, applied a method to calculate the shape of
the pubis for assessing "straight", "bowed", or even orientation criteria, with
or without the pubic boot or iliac peduncle, in a range of taxa. In
tyrannosaurids sensu lato, the pubis appears to have a large general curvature
on the anterior margin with a caudally bowed shaft between the boot and
peduncular region, yet the shaft is generally oriented "cranially," but whether
(or how) the boot and pedunculae affect the shaft curvature (maybe in assessing
possible diagnostic degrees of curvature), how the boot affect shaft
orientation, or where, in fact, the shaft ends and the boot begins.

<short mid-caudal prezygapophyses;>

  Which may influence the tail flexibility, and which would, if Paul is
correct, also reverses itself in some Avialae (*Archaeopteryx* has relatively
short prezygs, compared to some troodontids, *Rahonavis* as a possible
dromaeosaurid, and other dromaeosaurids, as well as the possible troodontid
*Buitreraptor*). Not that, of course, I think there is a way to correctly
assess variable or convergent characters, especially if they ARE
phylogenetically informative....

<retroarticular process present (though it is concave posteriorly as in
tyrannosaurids);>

  Are we talking about the large vertical process of the posterior/caudal
margin of the articular that butresses the quadrate when in articulation?

<sacral neural spines not fused into lamina;>

  Size based?

<Tarbosaurus has a posterior surangular foramen smaller than its promaxillary
fenestra too.>

  Is there any reason to suspect that the size of these foramina are correlated
at all?

<And I think Aviatyrannis' position is based on its large antitrochanter, which
could be due to distortion or breakage.>

  Or convergence.

  Cheers,

Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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